1. Technical Field
The present invention relates to a process for manufacturing a toner for the development of electrostatic latent image during the image formation by an electrophotographic method, for example. More particularly, the invention relates to a process whereby a mixture containing at least a synthetic resin with an acidic leaving group and a coloring agent is rendered water-dispersible by neutralizing the acidic leaving group in the synthetic resin with amine or alkali. The mixture is then mixed, stirred, and emulsified in an aqueous solution to produce a synthetic resin particle containing the coloring agent. The synthetic resin particle is preferably further aggregated to produce an aggregated resin particle, which is then washed.
2. Background Art
Two kinds of electrostatic latent image developer are known. One is the two-component developer that contains a toner particle and a carrier particle, and the other is the one-component developer containing a magnetic toner particle or a non-magnetic toner particle. The process for manufacturing developer toner particles can be divided into a dry process and a wet process. The dry process includes a pulverizing method whereby a binding resin and a coloring agent, for example, are kneaded, pulverized and then classified. The wet process includes a polymerization method whereby a coloring agent or the like is added during the polymerization of a binding resin. The wet process also includes an emulsion polymerization condensation method whereby a resin dispersion liquid is prepared by emulsion polymerization. The resin dispersion liquid is then mixed with a coloring-agent dispersion liquid comprising a solvent in which a coloring agent or the like is dispersed. The resultant aggregated particle is then heated and fused, thereby obtaining a toner. Another example of the wet process, a phase-inversion emulsification method, is disclosed in JP Patent No. 3063269. In this method, a coloring agent is dispersed and mixed in a solution in which a resin having an acidic group is dissolved in an organic solvent, and then the acidic group of the resin is neutralized by a base, thereby preparing a coloring-agent mixture. Water is added to emulsify the mixture, such that an encapsulated particle is produced in the water medium, which is then dried to obtain a toner.
If the wet process involves the step of producing a toner particle in an aqueous solution, impurities, such as a dispersing agent, emulsifier or flocculating agent, are used for the granulation of toner. As a result, the charging characteristics of the obtained toner has variations such that the amount of charge greatly differs depending on the environment in which the toner is used. It would also take time to remove these impurities by washing, which would require a large volume of water for washing.